Effect of Fibre Size on Mechanical Properties and Surface Roughness of PLA Composites by Using Fused Deposition Modelling (FDM)

Naturalfibre as a reinforcing agent has been widely used in many industrial applications.Nevertheless,several factors need to be considered,such as the size and weight percentage of thefibre used in binding.Using fused deposition modelling(FDM),this factor was investigated by varying the size of naturalfibre as the responding variable with afixed weight percentage of kenaffibre.The process of modifying the naturalfibre in terms of size might increase the dispersion of kenaffibre in the polymer matrix and increase the adhesion bonding between thefibre and matrix of composites,subsequently improving the interfacial bonding between these two phases.In this paper,the effect offibre size was evaluated by performing the mechanical test,Scanning Electron Micrograph(SEM)to observe the morphology of the composites,and also by surface analysis.The surface roughness was visualised using a 3D profilometer and thefigure was illustrated as colour shading in the image.The composite withfibre size≤100μm displayed better tensile andflexural strength,compared to other sizes.In conclusion,by reducing the size of thefibre,the composites could develop high strength performance for industrial applications.

基于FDM工艺的多功能3D打印机结构设计

该文针对传统3D打印机对于零部件的打印精度、加工效率以及许多异形曲面结构打印难以达到加工需求,且设备在运作时还会发热振动,产生噪音等问题进行优化,采用Creo软件设计一种基于熔融沉积制造(FDM)工艺且具备打印、打磨、清扫功能的3D打印机,并对多个零部件3D模型进行仿真和力学分析,分析喷头的温度场分布及五孔连接盖板、脚垫支架的受力分布。结果表明,该设计可实现减少耗材,降低发热振动,有效提高打印精度,缩短打印时间,结构稳定合理,具有较好的推广应用价值。

基于FDM 3D打印机机械结构和控制系统设计的研究

研究FDM技术支持下的3D打印机设计策略。使用步进控制精度在0.002 mm的丝杠滑块和步进电机的核心坐标控制系统,分别使用1组丝杠控制X轴和Y轴的定位,使用2组丝杠控制Z轴的定位,使用3组FDM挤出系统控制彩色打印过程,在探讨了坐标控制算法和冷却成型算法后,设计了一种包含7个执行机构且有LED综合状态显示功能的3D打印机机械结构和控制系统,且该系统可直接通过USB连接线从桌面端直接将文件传输到3D打印机的ARM系统中。基于FDM 3D打印机机械结构和控制系统设计的研究,可以得出:通过对坐标控制算法和冷却成型算法进行革新,提升对步进电机的控制策略,增加驱动程序可识别的3D模型文件种类,对FDM材料的成型过程进行进一步优化控制,是未来FDM技术支持下的3D打印机重点发展方向。

基于FDM工艺的3D打印制作手办探究

作为动漫周边衍生品的手办随着动漫产业的蓬勃发展,受到了很多动漫爱好者的喜爱,传统的手办制作工艺在设计、生产、版权等因素的影响下单个成本较高,且在设计风格上不一定符合动漫爱好者的审美喜好。随着3D打印技术的发展,桌面级打印机逐渐走进了普通人的生活中,使得动漫爱好者可以自行制作符合自己喜欢的手办。本文研究了传统手办制作的难点与3D打印制作手办的优势,并使用基于熔融沉积制造(Fused Deposition Modeling,FDM)工艺的3D打印机分析了手办制作过程中影响其质量的因素,提出了合理的方法提高3D打印制作手办的质量。

TPU导电丝材FDM打印及性能研究

为解决熔融沉积成型(FDM)打印器件力学性能低、功能性单一等问题,提出将聚氨酯(TPU)导电丝材用于FDM打印的方法,对打印件的力学性能、电磁屏蔽性能、压力传感性能进行了测试。结果表明:打印出的导电TPU试样表现出较好的力学性能,其抗拉强度为61.48 MPa,弹性模量为41.64 MPa,断裂伸长率为134.33%;在弯曲应变为10%时,弯曲强度为0.15 MPa,弹性模量为1.38 MPa,厚度为4 mm的打印试样在测试频率11.3 GHz时电磁屏蔽值为11.9 dB。制备的传感器工作范围为0~100 k Pa,其在0~10 kPa和10~100 kPa压力范围的灵敏度分别为0.107 kPa~(-1)和0.002 kPa~(-1),具有良好的稳定性和重复性。导电TPU丝材在电磁屏蔽、压力传感方面具有潜在的应用前景,拓宽了FDM打印的材料选择和应用潜力。

FDM连续挤压成型过程中温度场的有限元分析

在熔融沉积成型中,针对动态重新划分网格法描述金属流动变形存在计算复杂且工作量大的问题,提出一种连续挤压成型过程中温度场的有限元分析法。通过采用逐次单元法对熔丝在挤压槽内的应力进行分析,得出铝丝与轮槽各接触面上的热流密度,建立温度场有限元分析的数学模型。采用热流密度等效法对金属流动变形进行数值分析,减少计算时间,提高CPU效率。利用有限元分析软件对挤出喷头中的温度场进行热力耦合模拟仿真,获得在不同转速下挤压槽内温度场分布等值线图。仿真结果表明,熔丝在挤压成型过程中,温度场分布均匀,总体状态稳定,保证了成型质量,改进后程序运算时间减少30.9%,CPU运行效率优化17.3%。

一种新型六自由度FDM打印机结构方案设计

FDM技术(熔融层积成型技术)作为制造业企业运用最广泛的一项关键技术,在打印悬空、复杂几何形状试制件过程中产生大量的支撑结构,会造成打印丝材的浪费和降低打印效率,同时还会导致所打印的产品表面质量降低以及繁重的产品后处理工作。基于FDM龙门结构,通过增加打印平台2个旋转自由度和打印喷头的1个旋转自由度,提出了一种新型六自由度FDM打印机结构设计方案;并对打印平台和打印喷头的传动结构作进一步三维结构设计;对模型进行了仿真试验,验证了该装置能有效实现减少支撑结构效果,这对于FDM打印机结构设计优化提出了新的发展思路。

基于FDM的煤矿机械轴承劣化程度辨识

针对煤矿机械轴承运行过程中劣化程度较难确定致使无法针对性地进行维护更换的问题,提出了基于傅里叶分解方法(FDM)的煤矿机械轴承劣化程度辨识方法。首先对齿轮箱轴承中不同劣化程度的振动信号进行FDM分解,进而得到一系列傅里叶固有频带函数分量;然后通过各分量与原信号的相关度分析,筛选出优选分量,并对其进行奇异值分解得到一系列奇异值特征向量;最后将各劣化程度对应的奇异值特征向量作为极限学习机(ELM)的输入进行轴承劣化程度的辨识。实验结果表明,该方法能较好地应用于轴承的劣化程度辨识,对轴承的预知性维护、更换具有较大的现实意义。

FDM技术打印参数对成型效率的影响研究

FDM技术可用于工业领域中大型零件模型的打印,提升成型效率成为重要的研究课题。本研究通过响应面分析方法,探究了FDM打印参数对聚乳酸圆柱件成型效率的影响规律,得到了最优打印参数,并经过实际打印验证。结果表明层厚增加,成型效率提高;打印速度增加,成型效率提高;填充率增加,成型效率降低;路径规划和壁厚对成型效率影响不大。影响成型效率的因素按照顺序排列是:层厚>打印速度>填充率,其中层厚和打印速度影响显著。最优打印参数为打印速度85mm·s^(-1)、层厚0.175mm、填充率55%,预测时间为58.8min,实际时间为59min,预测精度达99.7%,为提升成型效率提供了依据。

Numerical analysis of high‑speed railway slab tracks using calibrated and validated 3D time‑domain modelling

Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks,provide safe and smooth rides,and reduce the maintenance frequency.In this paper,the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in Abaqus.It is then compared to the performance of a ballasted track.First,slab and ballasted track models are developed to replicate the full-scale testing of track sections.Once the models are calibrated with the experimental results,the novel slab model is developed and compared against the calibrated slab track results.The slab and ballasted track models are then extended to create linear dynamic models,considering the track geodynamics,and simulating train passages at various speeds,for which the Ledsgard documented case was used to validate the models.Trains travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil,considering the issues associated with critical speeds.Various train loading methods are discussed,and the most practical approach is retained and described.Moreover,correlations are made between the geotechnical parameters of modern high-speed rail and conventional standards.It is found that considering the same ground condition,the slab track deflections are considerably smaller than those of the ballasted track at high speeds,while they show similar behaviour at low speeds.

Hydrological Modelling of the Casamance River in Its Upstream Section (Basin at Kolda Level) to Predict Its Future States as a Function of Different Stresses

Flow records for stations in the Casamance basin are incomplete. Several gaps were noted over the 1980-2021 study period, making this study tedious. The aim of this study is to assess the potential impact of climate change on the flow of the Casamance watershed at Kolda. To this end, hydrological series are simulated and then extended using the GR2M rainfall-runoff model, with a monthly time step. Projected climate data are derived from a multi-model ensemble under scenarios SSP2-4.5 (scenario with additional radiative forcing of 4.5 W/m2 by 2099) and SSP5-8.5 (scenario with additional radiative forcing of 8.5 W/m2 by 2099). An analysis of the homogeneity of the rainfall data series from the Kolda station was carried out using KhronoStat software. The Casamance watershed was then delimited using ArcGIS to determine the morphometric parameters of the basin, which will be decisive for the rest of the work. Next, monthly evapotranspiration was calculated using the formula proposed by Oudin et al. This, together with rainfall and runoff, forms the input data for the model. The GR2M model was then calibrated and cross-validated using various simulations to assess its performance and robustness in the Casamance watershed. The version of the model with the calibrated parameters will make it possible to extend Casamance river flows to 2099. This simulation of future flows with GR2M shows a decrease in the flow of the Casamance at Kolda with the two scenarios SSP2-4.5 and SSP5-8.5 during the rainy period, and almost zero flows during the dry season from the period 2040-2059.

Modelling Land Use/Land Cover Change of River Rwizi Catchment, South-Western Uganda Using GIS and Markov Chain Model

Analysis of catchment Land use/Land cover (LULC) change is a vital tool in ensuring sustainable catchment management. The study analyzed land use/land cover changes in the Rwizi catchment, south western Uganda from 1989-2019 and projected the trend by 2040. Landsat images, field observations, key informant interviews and focus group discussions were used to collect data. Changes in cropland, forestland, built up area, grazing land, wetland and open water bodies were analyzed in ArcGIS version 10.2.2 and ERDAS IMAGINE 14 software and a Markov chain model. All the LULC classes increased in area except grazing land. Forest land and builtup area between 2009-2019 increased by 370.03% and 229.53% respectively. Projections revealed an increase in forest land and builtup area by 2030 and only built up area by 2040. LULCC in the catchment results from population pressure, reduced soil fertility and high value of agricultural products.

基于工业级FDM 3D打印的汽车车门设计及制造

基于工业级FDM 3D打印技术,以汽车车门为研究对象,提出Z+方向和Z-方向两种打印方案。分析车门结构特征,利用CATIA软件完成汽车车门的创新设计,并用自主研发的EDP-01工业级FDM 3D打印设备完成车门缩比模型的打印。两种方案打印分别耗时16 h和10 h,大幅度缩短了制造周期及研发成本;通过对两种方案的打印件进行质量评估,确定最终打印方案,并提交客户。

Implication of community-level ecophysiological parameterization to modelling ecosystem productivity:a case study across nine contrasting forest sites in eastern China

Parameterization is a critical step in modelling ecosystem dynamics.However,assigning parameter values can be a technical challenge for structurally complex natural plant communities;uncertainties in model simulations often arise from inappropriate model parameterization.Here we compared five methods for defining community-level specific leaf area(SLA)and leaf C:N across nine contrasting forest sites along the North-South Transect of Eastern China,including biomass-weighted average for the entire plant community(AP_BW)and four simplified selective sampling(biomass-weighted average over five dominant tree species[5DT_BW],basal area weighted average over five dominant tree species[5DT_AW],biomass-weighted average over all tree species[AT_BW]and basal area weighted average over all tree species[AT_AW]).We found that the default values for SLA and leaf C:N embedded in the Biome-BGC v4.2 were higher than the five computational methods produced across the nine sites,with deviations ranging from 28.0 to 73.3%.In addition,there were only slight deviations(<10%)between the whole plant community sampling(AP_BW)predicted NPP and the four simplified selective sampling methods,and no significant difference between the predictions of AT_BW and AP_BW except the Shennongjia site.The findings in this study highlights the critical importance of computational strategies for community-level parameterization in ecosystem process modelling,and will support the choice of parameterization methods.

Prospect Theory Based Individual Irrationality Modelling and Behavior Inducement in Pandemic Control

Understanding and modeling individuals’behaviors during epidemics is crucial for effective epidemic control.However,existing research ignores the impact of users’irrationality on decision-making in the epidemic.Meanwhile,existing disease control methods often assume users’full compliance with measures like mandatory isolation,which does not align with the actual situation.To address these issues,this paper proposes a prospect theorybased framework to model users’decision-making process in epidemics and analyzes how irrationality affects individuals’behaviors and epidemic dynamics.According to the analysis results,irrationality tends to prompt conservative behaviors when the infection risk is low but encourages risk-seeking behaviors when the risk is high.Then,this paper proposes a behavior inducement algorithm to guide individuals’behaviors and control the spread of disease.Simulations and real user tests validate our analysis,and simulation results show that the proposed behavior inducement algorithm can effectively guide individuals’behavior.

Modelling analysis embodies drastic transition among global potential natural vegetations in face of changing climate

Potential natural vegetation(PNV)is a valuable reference for ecosystem renovation and has garnered increasing attention worldwide.However,there is limited knowledge on the spatio-temporal distributions,transitional processes,and underlying mechanisms of global natural vegetation,particularly in the case of ongoing climate warming.In this study,we visualize the spatio-temporal pattern and inter-transition procedure of global PNV,analyse the shifting distances and directions of global PNV under the influence of climatic disturbance,and explore the mechanisms of global PNV in response to temperature and precipitation fluctuations.To achieve this,we utilize meteorological data,mainly temperature and precipitation,from six phases:the Last Inter-Glacial(LIG),the Last Glacial Maximum(LGM),the Mid Holocene(MH),the Present Day(PD),2030(20212040)and 2090(2081–2100),and employ a widely-accepted comprehensive and sequential classification sy–stem(CSCS)for global PNV classification.We find that the spatial patterns of five PNV groups(forest,shrubland,savanna,grassland and tundra)generally align with their respective ecotopes,although their distributions have shifted due to fluctuating temperature and precipitation.Notably,we observe an unexpected transition between tundra and savanna despite their geographical distance.The shifts in distance and direction of five PNV groups are mainly driven by temperature and precipitation,although there is heterogeneity among these shifts for each group.Indeed,the heterogeneity observed among different global PNV groups suggests that they may possess varying capacities to adjust to and withstand the impacts of changing climate.The spatio-temporal distributions,mutual transitions and shift tendencies of global PNV and its underlying mechanism in face of changing climate,as revealed in this study,can significantly contribute to the development of strategies for mitigating warming and promoting re-vegetation in degraded regions worldwide.

浅析不同颜色的PLA线材对FDM工艺参数的影响

随着3D打印技术的发展以及3D打印线材的不断研究与开发,近几年市场出现了各种颜色、不同填料的3D打印线材,大大提高了3D打印样件强度、表面精度和结构的表现性。然而,不同颜色和填料的复合线材在打印过程中参数设置的要求也各不相同。如果设置不合理将会出现断层、翘曲、开裂、堵头等现象,导致打印失败。本文结合工作中出现的一些问题,通过测试,找到不同颜色的复合线材聚乳酸(polylactic acid,PLA)在熔丝沉积成型(fused deposition modeling,FDM)技术打印时的工艺参数设置规律。

Investigation of Maxima Assumptions in Modelling Tropical Cyclone- Induced Hazards in the South China Sea

The present study aims to examine the suitability of two commonly used assumptions that simplify modelling metoceanconditions for designing offshore wind turbines in the South China Sea (SCS). The first assumption assumes thatjoint N-year extreme wind and wave events can be independently estimated and subsequently combined. The secondone assumes peak wind and waves can be modelled as occurring simultaneously during a tropical cyclone (TC) event.To better understand the potential TC activity, a set of 10000 years synthetic TC events are generated. The wind fieldmodel and the Mike 21 spectral wave model are employed to model the TC-induced hazards. Subsequently, theeffect of the assumptions is evaluated by analyzing the peak structural response of both monopile and semisubmersibleoffshore wind turbines during TC events. The results demonstrate that the examined assumptions are generally accurate.By assessing the implications of these assumptions, valuable insights are obtained, which can inform andimprove the modelling of TC-induced hazards in the SCS region.

Discrete Element Modelling of Damage Evolution of Concrete Considering Meso-Structure of ITZ

The mechanical properties of interfacial transition zones(ITZs)have traditionally been simplified by reducing the stiffness of cement in previous simulation methods.A novel approach based on the discrete element method(DEM)has been developed for modeling concrete.This new approach efficiently simulates the meso-structure of ITZs,accurately capturing their heterogeneous properties.Validation against established uniaxial compression experiments confirms the precision of thismodel.The proposedmodel canmodel the process of damage evolution containing cracks initiation,propagation and penetration.Under increasing loads,cracks within ITZs progressively accumulate,culminating in macroscopic fractures that traverse themortarmatrix,forming the complex,serpentine path of cracks.This study reveals four distinct displacement patterns:tensile compliant,tensile opposite,mixed tensile-shear,and shear opposite patterns,each indicative of different stages in concrete’s damage evolution.The widening angle of these patterns delineates the progression of cracks,with the tensile compliant pattern signaling the initial crack appearance and the shear opposite pattern indicating the concrete model’s ultimate failure.

A framework for dynamic modelling of railway track switches considering the switch blades,actuators and control systems

The main contribution of this paper is the development and demonstration of a novel methodology that can be followed to develop a simulation twin of a railway track switch system to test the functionality in a digital environment.This is important because,globally,railway track switches are used to allow trains to change routes;they are a key part of all railway networks.However,because track switches are single points of failure and safety-critical,their inability to operate correctly can cause significant delays and concomitant costs.In order to better understand the dynamic behaviour of switches during operation,this paper has developed a full simulation twin of a complete track switch system.The approach fuses finite element for the rail bending and motion,with physics-based models of the electromechanical actuator system and the control system.Hence,it provides researchers and engineers the opportunity to explore and understand the design space around the dynamic operation of new switches and switch machines before they are built.This is useful for looking at the modification or monitoring of existing switches,and it becomes even more important when new switch concepts are being considered and evaluated.The simulation is capable of running in real time or faster meaning designs can be iterated and checked interactively.The paper describes the modelling approach,demonstrates the methodology by developing the system model for a novel“REPOINT”switch system,and evaluates the system level performance against the dynamic performance requirements for the switch.In the context of that case study,it is found that the proposed new actuation system as designed can meet(and exceed)the system performance requirements,and that the fault tolerance built into the actuation ensures continued operation after a single actuator failure.